1. Field of the Invention
This invention relates to a method of depositing planarized silicon nitride and silicon oxide films on semiconductors without the use of chemical mechanical polishing (CMP).
2. Discussion of the Related Art
Planarization of semiconductor wafer surfaces up to a feature height has many useful applications in semiconductor manufacturing, such as the ability, with regard to MOSFETS, to implant gate/sources independently of gates and even to replace gates altogether. Typically, when a semiconductor device gate or other protruding feature is to be removed, etched, or doped or subjected to some other processing, surrounding source and drain regions or other sensitive areas are protected by laying down a layer of tetraethoxysilane, tetraethylorthosilicate, tetraethelorthosilicate, or tetrethoxysilicide, any of which is referred to in the semiconductor art as TEOS. Other protective oxides used in the art include spin-on-oxides and borophosphosilicate (BPSG) glass. After deposition of these oxides, it is necessary to planarize the TEOS layer down to the gate so as to expose the gate for subsequent processing. The planarizing is usually accomplished by chemical mechanical polishing (CMP). Aside from the disadvantage of having to perform a CMP operation, CMPs have other disadvantages. For one, CMP operations cause dishing in the oxide when the gates are spaced relatively far apart. Dishing can lead to shorts developing between the gates during gate replacement operations because new gate material is deposited in the dished areas. Dishing can also cause penetration of an implant through the TEOS into the underlying layer.
Disclosed is a method of obtaining thermally stable planarizing films while exposing structures for further processing, the method comprising depositing a planarizing silicon compound film, selected from the group silicon oxide and silicon nitride, depositing a planarized organic polymer film to a thickness effective in protecting the silicon compound film to a thickness effective in leaving silicon compound excess exposed, and etching away the silicon compound excess so as to expose the underlying structures.
In a further aspect of the invention, the organic polymer film is then removed.
In another aspect of the invention, the planarizing silicon compound film is deposited by high density plasma chemical vapor deposition.
In another aspect of the invention, the organic polymer film comprises a photoresist.
In another aspect of the invention, the organic polymer film comprises an anti-reflective coating.
In another aspect of the invention, the organic polymer film comprises a novolak resin.
In another aspect of the invention, the organic polymer film comprises an organic polymer selected from a novolak resin, a copolymer of benzophenone and bisphenol-A, a film formed from an organic solution of multifunctional acrylates and methacrylate monomers, polyurea, and polysulfone.
In another aspect of the invention, said depositing of a planarized organic polymer film further comprises depositing a layer of organic polymer to a thickness sufficient to cover said excess and then etching back said organic polymer so as to expose said excess.
In another aspect of the invention, the organic polymer film is formed by the method of depositing a conformal organic polymer on the substrate and planarizing the resulting conformal organic polymer film by chemical mechanical polishing.
In another aspect of the invention, the underlying structures comprise silicon or polysilicon.
In another aspect of the invention, the underlying structures comprise metal, the planarizing silicon compound film is silicon nitride, and the etching away of the silicon compound excess comprises a phosphoric acid etch.
In another aspect of the invention, the underlying structures comprise metal, the planarizing silicon compound film is silicon nitride, and the etching away of the silicon compound excess comprises a sodium hydroxide etch.
In another aspect of the invention, the underlying structures comprise metal, the planarizing silicon compound film is silicon oxide, and the etching away of the silicon compound excess comprises a dry plasma methane/methyl-trifluoride etch.